The present invention generally relates to a dielectric resonator with an earth electrode and a resonance electrode being formed on a dielectric base plate or a dielectric block, and a manufacturing method thereof.
A dielectric resonator having resonance electrodes (internal conductors) formed within a dielectric block, and earth electrodes (external conductors) formed on the outside face of a dielectric block is known. Also known is a dielectric resonator having resonance electrodes (strip lines) formed on one surface of a dielectric base plate and earth electrodes formed on an opposite surface. Such resonators are used as filters and so on in, for example, microwave bands.
Coils for connecting resonators, capacitors and base plates and so on for mounting them, together with a plurality of dielectric resonators, capacitors and base plates and so on are accommodated within a case in a dielectric filter of a discrete type which includes, for example, a plurality of dielectric resonators.
Various types of dielectric resonators, coils and capacitors are used in accordance with the required specifications in the dielectric filters of such construction.
In an integrated type of dielectric filter, a plurality of resonators are constructed on a dielectric block which is integral from the beginning, or which is integrated by the assembling operation, and correspond to a plurality of stages of dielectric filters and so on.
A transmission filter and a reception filter are used in a transceiver sharing device in, for example, the microwave band. Characteristics such as a smaller damping amount in the transmission band and yet a sufficiently large damping amount in the transmission band are required in the reception filters. It is effective to provide a pole (hereinafter referred to as polarization) as an effective method in the designing of a band pass filter capable of having a given damping amount in a frequency zone generally away from the pass band width.
In the dielectric filter of the conventional construction, it is not suitable for a dielectric filter to be of a type which mounts on the surface of, for example, a basic plate, because the terminal for coupling use has to be inserted from the outside into the resonance electrode formed hole so as to interconnect the resonators of the given stages. Also, special parts are required for the operation is in order to directly effect the electromagnetic connection among its front, rear resonators with the resonator of one or more stages being bypassed.
A dielectric resonator of a surface mounting type as shown in FIG. 65 and FIG. 66 is taken into consideration in connection with the present application and has been disclosed in Japanese Patent Laid-Open Publication No. 3-303366.
FIG. 65 is a perspective view of a dielectric resonator. FIG. 66 is a top face view of the dielectric resonator. In FIG. 65, reference numerals 102, 103 are respectively dielectric base plates. Sectional semi-circular shaped grooves 105, 106, 107, 108, 109 are provided respectively on a first main face (a face opposite to the dielectric base plate 103) of the dielectric base plate 102 and the first main face (a face opposite to the dielectric base plate 102) of the dielectric base plate 103, with internal conductors being respectively formed on the inside faces thereof. Signal input, output electrodes (115 and so on) are formed across the second main face (bottom face in the drawing) from two side faces of the dielectric base plates 103. Coupling electrodes E10 are formed on a given region of the second main face (top face in the drawing) of the dielectric base plate 102. An external conductor 112 is formed on the external surfaces of the dielectric base plates 102, 103 except for the regions of the above described signal input, output electrodes (115 and so on) and the coupling electrodes E10. As shown in FIG. 66, the coupling electrodes E10 effect the respective capacity connection between the open end vicinity of the internal conductors 117, 119 within the internal formed holes 106, 108. By such construction, the second stage and the fourth stage among the band pass filters of five stages are interconnected so as to cause the damping pole on the low-pass side of the pass band width.
The dielectric resonators shown in FIG. 65 and FIG. 66 can be provided with poles without addition of special parts, with a large operational advantage, in that the surface mounting operation can be effected on the circuit base plate together with the electronic parts of the other surface mounting type. However, in such conventional dielectric filter as shown in FIG. 65 and FIG. 66, the Qo value of the resonator is lower, thus resulting in a danger of deteriorating the insertion loss characteristics of the filter, because the current flowing through the external conductor 112 is interrupted in the region where the coupling electrode E10 is formed. As the coupling electrode formed region becomes an open portion of the external conductor, some electromagnetic field leakage is caused, so that the influence of a metallic unit adjacent to the dielectric filter may become a problem.
In a dielectric filter of the conventional discrete type, individual parts such as coils, capacitors or the like are required together with a plurality of dielectric resonators, with a defect that the whole becomes larger in size as the number of the parts increases, and the assembling operation step is complicated. In the conventional integral type of dielectric filter, only the filter of the characteristics restricted is provided in the pattern formation of the resonance electrode or the earth electrode although the above described defects are not provided. When the plan circuit and so on are constructed with one portion of the earth electrode (external conductors) being patterned, some measures are required to be taken with respect to the electromagnetic leakage.
Also, in the conventional dielectric filter, there is danger of lowering the Qo value of the resonator, deteriorating the insertion loss characteristics of the filter, because the current flowing through the external conductor is interrupted in the region of the coupling electrode. As the coupling electrode region is an opening portion of the external conductor, there is danger of causing some electromagnetic leakage, which causes a problem of influence by the metallic unit adjacent to the dielectric filter.
In the conventional dielectric filter, the respective base plate, capacitor element and coil parts are necessary and further, a soldering operation for engaging the respective parts is required, which causes the problems that the cost rises and also, the productivity is lower.
Further, since the pole-providing electrode is formed within the region of the earth electrode with one portion of the earth electrode of the dielectric base plate being shaved off to form the conventional polarized construction, the earth current flowing through the above described earth electrode is interrupted in the above described gap portion, which causes a problem that the Qo value of the resonance electrode is deteriorated, and the characteristics of insertion loss are lowered.